1. Field of the Invention
The present invention generally relates to a photo-mask and a photo-mask pair, and more particularly to a photo-mask and a photo-mask pair improved so as to enhance an ability of ensuring dimension accuracy. The present invention further relates to a semiconductor device formed to use such a photo-mask and to a method of manufacturing such a semiconductor device.
2. Description of the Background Art
FIGS. 21A to 21F illustrate a cross-sectional view showing a method of manufacturing a semiconductor device using a conventional photo-mask, in particular, a process of forming an etching pattern of SiO2 film.
Referring to FIG. 21A, a SiO2 film 52 is formed on a silicon substrate 51.
Referring to FIG. 21B, a photo-resist 53 is formed on SiO2 film 52.
Referring to FIG. 21C, photo-resist 53 is selectively irradiated with UV rays using a photo-mask 54 to form a potential image in photo-resist 53.
Referring to FIG. 21D, photo-resist 53 is developed to form a resist pattern 55.
Referring to FIG. 21E, SiO2 film 52 is etched using resist pattern 55 as a mask.
Referring to FIGS. 21E and 21F, photo-resist pattern 55 is removed so that a pattern 56 of the SiO2 film remains on silicon semiconductor substrate 51.
FIG. 22 is a cross-sectional view of a photo-mask. Referring to FIG. 22, a light-shielding pattern 57 formed of a metal film, oxide, nitride, sulfide, or fluoride of Cr, Mo, Zr, Ta, W or the like and a compound thereof is provided on a glass substrate 58. Light-shielding pattern 57 has a film thickness of approximately 100 to approximately 170 nm. Such a photo-mask is provided, in addition to an actual pattern, with a monitor mark for ensuring the dimension of the actual pattern. The monitor mark is also formed of the metal film or the metal compound film described above.
FIG. 23 is a plan view of a conventional photo-mask.
A mask pattern region 2 is formed on a photo-mask 1. A semiconductor element chip region 3 is provided in mask pattern region 2. Memory cell region 3a (a high-density portion) is provided in semiconductor element chip region 3. Semiconductor element chip region 3 is provided with an element pattern 5 for a high-density portion (such as a memory cell) and an element pattern 6 for a low-density portion (such as a low-density logic portion). Monitor mark 4 is provided at each of the four corners of mask pattern region 2. Monitor mark 4 is also provided at a middle point of a long side of mask pattern region 2.
Examples of conventional monitor marks are shown in FIGS. 24A and 24B. FIG. 24A is an example of a monitor mark formed with interconnections (hereinafter referred to as xe2x80x9cinterconnection typexe2x80x9d). FIG. 24 B shows a typical interconnection type element pattern in the actual pattern. The interconnection type monitor mark shown in FIG. 24A is configured to ensure the dimension of the interconnection type element pattern shown in FIG. 24B. The arrows in FIGS. 24A and 24B point the position where the dimension is measured.
FIGS. 25A and 25B are plan views of conventional monitor marks formed with holes (hereinafter referred to as xe2x80x9chole typexe2x80x9d). FIG. 25A shows an example of a hole type monitor mark and FIG. 25B shows a typical hole type element pattern in the actual pattern. The hole type monitor mark shown in FIG. 25A is for ensuring the dimension of the hole type element pattern shown in FIG. 25B.
FIG. 26 shows an example of a conventional cross mark for measuring registration accuracy.
In FIGS. 24A through 26, the portion designated by reference number 7 denotes an outer frame of the monitor mark and the portion designated by reference number 8 denotes a pattern region for which the element dimension is monitored. A cross pattern for registration accuracy measurement is designated by reference number 9.
Thus, the conventional monitor mark was formed to have a pattern shape of simple cross, line and space, rectangle or the like, which is simply designed to represent the pattern of the semiconductor element.
However, since a semiconductor element has been required to have improved function and performance, a system LSI in which a memory element and a logic element are mounted with high density has come to be designed along with size reduction of the pattern, thereby complicating the photo-mask used for manufacturing of these elements. In particular, the memory element pattern having higher density and smaller size and the logic element pattern having a large difference between coarse portion and dense portion of the pattern are arranged on the same photo-mask. Further, as a pattern is reduced in size, an error between the pattern dimension and the design dimension abruptly increases if the pattern has coarse and dense portions. Thus, it has been difficult for the simple pattern for monitoring dimension as shown in FIGS. 24A, 24B, 25A, 25B and 26 to represent the actual element pattern. It has therefore been difficult to ensure the photo-mask dimension with high accuracy. An example of the error is shown in Table 1.
In the conventional monitor mark, each element pattern was required to be individually measured in a process of manufacturing a photo-mask. However, such individual measurement of each element pattern takes too much effort, so that a method of making the mask with low cost and short delivery period has been desired.
The present invention is made to solve the problems described above, and an object of the invention is to provide a photo-mask improved to ensure the photo-mask dimension with high accuracy.
An another object of the invention is to provide photo-mask improved such that the photo-mask can be manufactured with low cost and short delivery period.
A further object of the invention is to provide a photo-mask pair, which enables efficient manufacturing of a semiconductor device.
A still further object of the invention is to provide a semiconductor device manufactured using such a photo-mask.
Another object of the invention is to provide a method of manufacturing the semiconductor device using such a photo-mask.
The photo-mask according to the first aspect includes a substrate. The substrate is provided with an actual pattern thereon. A monitor mark for ensuring the dimension of the actual pattern is provided on the substrate. The monitor mark is provided with a coarse pattern and a high-density pattern formed to have a density higher than the coarse pattern.
According to the invention, the monitor mark is provided with the coarse pattern and the high-density pattern formed to have a density higher than the coarse pattern, so that the dimension of the coarse portion of the actual pattern can be ensured and the dimension of the high-density portion of the actual pattern can also be ensured.
In the photo-mask according to the second aspect, the monitor mark is further provided with a cross pattern for registration accuracy measurement having a pair of arms crossing each other.
According to the invention, even the registration accuracy can be ensured. In the photo-mask according to the third aspect, the coarse pattern and the high-density pattern are each provided remote from a scanning region of the cross pattern.
According to the invention, the coarse pattern and the high-density pattern will not interrupt the scanning of the cross pattern.
In the photo-mask according to the fourth aspect, the monitor mark includes an outer frame pattern enclosing the coarse pattern and the high-density pattern. The outer frame pattern is formed wide enough to be visually recognizable through a microscope.
According to the invention, the existence of the monitor mark can be visually recognized through the microscope.
In the photo-mask according to the fifth aspect, a first dummy pattern having the same density as the coarse pattern is provided in the vicinity of the coarse pattern. A second dummy pattern having the same density as the high-density pattern is provided in the vicinity of the high-density pattern.
In the photo-mask according to the invention, the dummy patterns each having the same density as the high-density pattern or the coarse pattern are provided in the vicinity of the respective patterns, so that light can be evenly received at the time of exposure.
In the photo-mask according to the sixth aspect, a special-use pattern for a special use is provided in the vicinity of each of the high-density pattern and the coarse pattern.
In the photo-mask according to the invention, the special-use pattern is provided so that it can be utilized for a special use.
In the photo-mask according to the seventh aspect, the coarse pattern is formed as a single-line pattern, and the single-line pattern is at the same time the arm portion of the cross pattern.
According to the present invention, the area of the mask can effectively be utilized.
The photo-mask according to the eighth aspect includes a substrate. An actual pattern including a hole pattern is provided on the substrate. A monitor mark for ensuring the dimension of the hole pattern is also provided on the substrate. The monitor mark is provided with a cross pattern having a pair of arms crossing each other, a hole pattern ensuring pattern for ensuring the dimension of the hole pattern arranged remote from the scanning region of the cross pattern, and an outer frame pattern enclosing the cross pattern and the hole pattern ensuring pattern. The outer frame pattern is divided into multiple portions to avoid an over exposure. The arm portion of the cross pattern is also divided into multiple portions to avoid the over exposure.
According to the invention, the outer frame pattern is divided into multiple portions so as to avoid the over exposure. The arm portion of the cross pattern is also divided into multiple portions, so that the over exposure can be avoided.
The invention according to the ninth aspect involves a photo-mask pair including a first photo-mask used in a first step and a second photo-mask used in a second step subsequent to the first step. The first photo-mask includes a first substrate, a first actual pattern provided on the first substrate, and a first monitor mark provided on the first substrate for ensuring the dimension of the first actual pattern. The first monitor mark is provided with a first pattern for monitoring which represents the first actual pattern. The second photo-mask includes a second substrate, a second actual pattern provided on the second substrate, and a second monitor mark provided on the second substrate for ensuring the dimension of the second actual pattern. The second monitor mark is provided with a second pattern for monitoring which represents the second actual pattern. When the first photo-mask is used in the first step and the second photo-mask is used in the second step, the first pattern is provided in the first monitor mark and the second pattern is provided in the second monitor mark to avoid overlapping of the first and second patterns. The invention eliminates the generation of dust.
The invention according to the tenth aspect involves a photo-mask pair including a first photo-mask used in a first step and a second photo-mask used in a second step subsequent to the first step. The first photo-mask includes a first substrate, a first actual pattern provided on the first substrate, and a first-monitor mark provided on the first substrate to ensure the first actual pattern. The first monitor mark includes a first monitor pattern representing the first actual pattern. The second photo-mask includes a second substrate, a second actual pattern provided on the second substrate, and a second monitor mark provided on the second substrate to ensure the dimension of the second actual pattern. The second monitor mark includes a light-shielding pattern provided at a position where the first pattern can be entirely covered when the first photo-mask is used in the first step and the second photo-mask is used in the second step. The invention can eliminate the generation of dust.
The invention according to the eleventh aspect involves in a photo-mask pair including a first photo-mask used in a first step and a second photo-mask used in a second step subsequent to the first step. The first photo-mask includes a first substrate, a first actual pattern provided on the first substrate, and a first monitor mark provided on the first substrate to ensure the dimension of the first actual pattern. The first monitor mark includes a first cross pattern having a pair of arms crossing each other, and a first frame pattern provided to enclose the first cross pattern. The second photo-mask includes a second substrate, a second actual pattern, and a first monitor mark provided on the second substrate to ensure the dimension of the first actual pattern. The second monitor mark is provided with a second cross pattern having a pair of arms crossing each other in the cross shaped manner and a second frame pattern provided to enclose the second cross pattern. When the first photo-mask is used in the first step and the second photo-mask is used in the second step, the position and the width of the arms of the first cross pattern are selected such that one of the first and second arms entirely covers the other. The invention eliminates the generation of dust.
The photo-mask according to the twelfth aspect includes a substrate. A rectangular semiconductor element chip region in which a pattern of the semiconductor element is formed is provided on the substrate. A plurality of monitor marks for ensuring the dimension of the semiconductor element pattern are provided on the substrate and within the semiconductor device chip region. The plurality of monitor marks are provided at the four corners of the rectangular chip, at around the middle of two long sides of the rectangular chip, and at a position near the center of the rectangular chip, respectively. The invention eliminates the need for measuring the actual element pattern.
In a method of manufacturing a semiconductor device according to the thirteenth aspect, a photo-mask is first prepared including a substrate, an actual pattern provided on the substrate, and a monitor mark ensuring the dimension of the actual pattern, the monitor mark being provided with a coarse pattern and a high-density pattern formed to have a density higher than the coarse pattern. A semiconductor substrate is then prepared. A resist is formed on the semiconductor substrate. Thereafter, the photo-mask is used as a mask to expose the resist. The resist is then developed to form a resist pattern. The resist pattern is used to etch the semiconductor substrate. According to the invention, a highly reliable semiconductor device can be attained.
The invention according to the fourteenth aspect relates to a semiconductor device formed by at least steps (a) through (f) in the following:
(a) a step of preparing a photo-mask including a substrate, an actual pattern provided on the substrate, and a monitor mark for ensuring the dimension of the actual pattern, the monitor mark being provided with a coarse pattern and a high-density pattern having a density higher than the coarse pattern,
(b) a step of preparing a semiconductor substrate,
(c) a step of forming a resist on the semiconductor substrate,
(d) a step of using the photo-mask as a mask to expose the resist,
(e) a step of developing the resist to form a resist pattern, and
(f) a step of using the resist pattern to etch the semiconductor substrate.
According to the invention, a highly reliable semiconductor device can be attained.